One problem related to front suspension leaf spring u-bolt has been reported for the 2001 Ford Explorer Sport. The most recently reported issues are listed below.
Rear passenger side leaf spring was found to be cracked around bushings front and rear when removed for replacement. 3 Ford dealers and 3 other shops could not see this over a period of 90,000 miles. It wasn't till the bushings on the other side started to wear and I decided to replace the all the components that it was found when the leaf spring suddenly fell out after removing the u-bolts.